There are several known methods for measuring a cylinder volume of the combustion chamber of a reciprocation engine when a piston is at top dead center. The first method is to utilize the volume and pressure change of the medium inside the combustion chamber (JP H04-198833A, JP H06-082342A). The second method is an acoustic volume measuring method using a Helmholtz resonator (JP H06-186070A). The third method is to measure the quantity of the oil needed to fill the hollowed portion of the cylinder main body that is surrounded by the piston positioned at the top dead center and cylinder head. However, the first and second methods may have disadvantages that the pressure variation and the acoustic pressure cannot be measured accurately because the air leak may occur at a gap around the piston ring and the combustion chamber may not be a completely closed object. The third method has a disadvantage for use in a factory line because it is necessary to disassemble the cylinder main body.